1. Field of the Invention
This invention is directed to dispersions useful in preparing radiopharmaceutical scanning agents, to technetium labelled dispersions to methods for preparing such dispersions and to their use as scanning agents.
2. Description of the Prior Art
Technetium-99m sulfur colloids are used as scintillation scanning agents to image the reticuloendothelial system particularly the liver and spleen. They are ideal scanning agents for determining size, shape and anatomical position of the liver. Sulfur colloid particles are phagocytized by the Kupffer cells of the liver. Unlike radiopharmaceuticals which are rapidly excreted by the liver, the phagocytized sulfur colloid particles remain fixed by the Kupffer cells during the scanning period and lend to more technically uniform liver imaging. Areas of the liver scan demonstrating filling defects (reduced radioactivity) suggest the possibility of hepatic anomalies. It is possible through scanning to follow a therapeutic regimen of a diagnosed hepatic lesion.
As in the liver, sulfur colloids are phagocytized by the reticuloendothelial cells of the spleen. The imaging of the spleen has proved to be of clinical importance particularly in detection of splenomegaly. This accumulation in the spleen is of clinical value because splenomegaly is often accompanied by or is a result of hepatomegaly. Like the liver, splenic scanning can be used as a follow-up to show the results of therapeutic regimens.
Known methods for preparing technetium sulfur colloids have been practiced widely for many years. Traditionally they have been prepared extemporaneously by bubbling hydrogen sulfide through an acidified solution of sodium pertechnetate and then raising the pH from 5 to 7. Partly because of the toxicity of unreacted hydrogen sulfide and secondly to enable preparation of technetium sulfur colloid from commercial kits a second extemporaneous preparation was devised. In this preparation sodium pertechnetate injection, acidified with a mineral acid, is added to sodium thiosulfate and the solution heated. A technetium sulfur colloid is formed which is buffered to 5 to 7 and stabilized with gelatin. However, commercial kits utilizing this procedure, as is described in U.S. Pat. No. 3,683,066, requires the technician to carry out a number of steps as well as to use three separate reaction vials. Other technetium sulfur colloid procedures are described in U.S. Pat. No. 3,810,976 and 3,720,761.
While these procedures may be useful for clinical use, their usefulness is somewhat limited because such methods are time consuming and/or require a large number of procedural operations on the part of the technician which may introduce errors and affect the accuracy of the product. Thus commercially available kits typically contain a plurality of reagents and their clinical use requires the technician to perform many time consuming operations in preparing the reagents.
Consequently a pharmaceutical preparation that may be rapidly radio labelled with fewer procedural operations on the part of the technician would be an advancement in the art.